The photoreceptors are the visual system transducers which convert light energy into electrical signals. It is these electrical signals that are conducted from the receptors to the rest of the visual system. The electrical signals produced in the receptors are immediately influenced by electrotonic and chemical synaptic interactions with other photoreceptors. Thus, any rod or cone can be excited by light striking adjacent rods or cones. The electrical signal generated in the photoreceptors is transmitted to bipolar cells by way of a chemical synapse. This synapse is important for determining the sensitivity of the entire visual system. An electrophysiological approach using intracellular microelectrodes will be used to record the potentials of rods, cones and bipolar cells. We will be studying the synaptic transmission from receptor cells to bipolar cells and will determine the nature and underlying mechanisms of this signal transfer. Noise analysis techniques will be employed in this study. We will also investigate and determine the nature of the membrane properties of the rods and cones. An enzymatic isolation procedure will be used to separate and study individual cells. These membrane properties affect the degree of interaction between receptors so knowledge of their nature and characteristics will enable us to understand the details of the interactions. We will also be studying the spatial properties of adaptation in the rod network and the mechanisms underlying the antagonistic feedback from horizontal cells to cones.